puppet: Install the same version of postgres-client as the server.

We require a `pg_dump` whose version matches the version of the server
we are configured against (see 3a8b4b0205).  Installing the latest
`postgresql-client` does not guarantee that we have such a binary
present.

docs/production/postgresql.md

@@ -48,6 +48,14 @@ PostgreSQL documentation):
     overhead. I want to be sure that I connect to a server I trust,
     and that it's the one I specify.
 
+Set the remote server's PostgreSQL version in `/etc/zulip/zulip.conf`:
+
+```ini
+[postgresql]
+# Set this to match the version running on your remote PostgreSQL server
+version = 16
+```
+
 Then you should specify the password of the user zulip for the
 database in /etc/zulip/zulip-secrets.conf:
 

puppet/kandra/manifests/prometheus/postgresql.pp

@@ -49,7 +49,7 @@ class kandra::prometheus::postgresql {
 
   include zulip::postgresql_client
   exec { 'create prometheus postgres user':
-    require => Package['postgresql-client'],
+    require => Class['zulip::postgresql_client'],
     command => '/usr/bin/createuser -g pg_monitor prometheus',
     unless  => 'test -f /usr/bin/psql && /usr/bin/psql -tAc "select usename from pg_user" | /bin/grep -xq prometheus',
     user    => 'postgres',

puppet/zulip/manifests/postgresql_client.pp

@@ -1,8 +1,6 @@
 class zulip::postgresql_client {
-  # This may get us a more recent client than the database server is
+  include zulip::postgresql_common
-  # configured to be, ($zulip::postgresql_common::version), but
+  package { "postgresql-client-${zulip::postgresql_common::version}":
-  # they're compatible.
-  package { 'postgresql-client':
     ensure => installed,
   }
 }